I have seen fish swim through little castles. If these castles had three or four exits then a laserpointerish graphic on the side of the tank could change its geometry or dapple.
The fish would start to swim in a way that optimized their experience. Advanced users might go genetic algorithm on the thing as well, modifying the patterns further with hue, brightness, and geometry all fish adjustable.-- beanangel, Jan 06 2018 This would almost certainly work with cephalopods that use chromatophores for visual communication.
Bony fish, maybe not so much.-- 8th of 7, Jan 07 2018 Sp.: chromatophore.-- MaxwellBuchanan, Jan 07 2018 Sp. fixed.
Autocorrect dictionary edited.-- 8th of 7, Jan 07 2018 Could be even more fun if you had an octopus with a disco-ball. [marked-for-tagline]-- RayfordSteele, Jan 09 2018 random, halfbakery